Lab #5: Cellular Respiration
Ananya, Bonnie, Jiaqi,
Neha, and Susie
Purpose of this Lab
The purpose of this lab was to determine the rate of cellular respiration in germinating peas by
measuring the consumption of oxygen at various temperatures.
How can the rate of cellular respiration be measured?
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By measuring the amount of glucose consumed
By measuring the amount of oxygen consumed
By measuring the amount of carbon dioxide produced
How did you measure rate of cellular respiration in this lab?
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The rate of cellular respiration of germinating peas was found by measuring the oxygen that
was consumed over time
Relevance of the Lab to Class Content
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Cellular Respiration
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C₆H₁₂O₆ + 6O₂ ⟶ 6CO₂ + 6H₂O + Energy (ATP + energy)
Plants use cell respiration when there is a lack of light to perform cell
work
The rate of cellular respiration accelerates as enzymes begin using the
stored food supply to generate ATP.
Other concepts within the Lab
-
Gas Law: PV = nRT
Respirometer works in accordance to the gas law:
Experimental Design Diagram
IV: Type of peas
(germinating and dry)
DV: Pressure of gas
Levels of IV: 1
# of trials: 6
Control: Beads
Constant: Temperature,
volume of peas, cotton
balls
Hypothesis
-
Null Hypothesis: The rate of cellular respiration will be the same in the
germinating peas and the non-germinating peas and beads and the rate
of cellular respiration will be the same at 10 degrees C and 25 degrees C
-
Our hypothesis: The rate of cellular respiration will be greater in
germinating peas than in non-germinating peas, and greater at 25
degrees C.
Procedure
4. Place 10 drops of KOH on
absorbent cotton, then put rope
cotton over
1.
2.
3.
Measure 25 germinating peas
Measure 10 dry peas + enough
glass beads for the same
volume
Measure glass beads with a
volume = volume of the
germinating peas
5. Equilibrium step
6. Check water temperature (10C or 25C)
7. Place respirometers in water, measure
every 5 min
***Optional Step: place food dye on
tip of respirometer to see bubble
better
Presentation of Data - Personal Data
Personal Data (Raw Data)
Personal Data (Corrected Difference)
Time
(minutes)
10℃ Germinating
Peas (mL O2)
10℃ Dry Peas
(mL O2)
Time
(minutes)
10℃ Germinating
Peas (mL O2)
10℃ Dry Peas
(mL O2)
0 minutes
0 mL
0 mL
0 minutes
0 mL
0 mL
5 minutes
N/A
N/A
5 minutes
N/A
N/A
10 minutes
0.73 mL
0.39 mL
10 minutes
-0.24 mL
0.11 mL
15 minutes
0.74 mL
0.27 mL
15 minutes
-0.32 mL
0.14 mL
20 minutes
0.74 mL
0.25 mL
20 minutes
-0.42 mL
0.18 mL
Presentation of Data - Class Data
***Without Outliers’ Number in GREEN
Class Data of Corrected Differences (Averages)
Time (minutes)
10℃ Germinating
Peas (mL O2)
10℃ Dry Peas
(mL O2)
25℃ Germinating
Peas (mL O2)
25℃ Dry Peas
(mL O2)
0 minutes
0 mL
0 mL
0 mL
0 mL
5 minutes
-0.27 mL
0.14 mL
0.78 mL
10 minutes
-0.33 mL
0.20 mL
1.19 mL
0.64 mL -0.07
15 minutes
-0.47 mL
0.11 mL
1.49 mL
0.69 mL -0.05
20 minutes
-0.52 mL
0.15 mL
1.76 mL
0.67 mL -0.08
-0.20
0.14
0.62 mL -0.06
Group Graph of Germinating Peas
Group Graph of Dry Peas
Error Analysis
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Not being able to see the bubble and therefore missing data points
Proper procedure is to read the bottom of the meniscus and groups that
read the top of meniscus have inaccurate data
Moving the vials after the experiment started could have lead to
inaccurate results
Not having the same amount of cotton in each vial
Reading errors
Reading before or after exact time
0.73 (correct) vs. 7.3 (incorrect), leads to outliers
Unable to maintain temperature in water bath
Conclusion
-
Germinating peas consumed more oxygen at a faster rate than the nongerminating peas
Non-germinating peas don’t require as much oxygen therefore having a
lower rate of respiration
Respiration rates increase as the temperature increases
Temperature and respiration rates are directly proportional to each other
Class Discussion
PV = nRT
1. Using the ideal gas law and the experience from
this lab, give the variables that had to be
controlled for your data.
P = Pressure changes (DV)
V = Volume remains constant
n = moles remains the same as there is the
same volume of substance
R = gas constant stays constant
T = Temperature was the changed factor (IV)
2. Describe and explain the relationship between
the amount of O2 consumed and time based on the
data.
Actual: No trend in data
Supposed to be: As time goes on, the amount
of oxygen consumed increases
3. Why was it necessary to correct the readings
from the peas with the readings from the beads?
-Numerical comparison of the peas to the beads (control)
-Changes in the environment such as changes in
atmospheric pressure affected the rate of respiration, so
the readings were corrected so that the results could be
the most accurate
-For a more accurate comparison between the two types
of seeds
4. What was the purpose of the
KOH in the experiment?
CO₂ + 2KOH ---> K₂CO₃ + H₂O
The purpose of the KOH was to react with the CO₂ and
form a precipitate so that it doesn’t mess with the gas
pressure of O₂ entering the device when CO₂ tries to be
released.
5. Explain why water moved into the
respirometers.
The water moved into the respirometers
because O₂ entered the device and due to
lower pressure, the water entered the device
6. If you used the same experimental design to
compare the rates of respiration of a 25 g reptile
and a 25 g mammal at 10°C, what results
would you expect? Explain
Mammals have a higher rate of respiration
Reptiles are cold blooded and can survive in
lower temperatures
Mammals will respire more to keep their
higher temperature in 10 degrees (produce
more ATP to keep warm)
7. If respiration in a small mammal was studied at
both room temperature (25°C) and 10°C, what
results would you predict? Explain
Higher at 10 degrees because they have to
respirate more to create more ATP to maintain
the high body temperature
Not as much respiration needed at 25 degrees
because it is warmer and not as much temp
regulation needed
8. What results would you expect if you designed
an experiment to examine the rates of cellular
respiration with peas that have been germinating
different lengths of times: 0, 24, 48, & 72 hours?
Explain.
The peas that were germinating for 0 hours
will have the lowest rate of cellular respiration.
As time goes on, rate of cellular respiration
increases. The peas that were germinating for
72 hours will have the greatest rate of cellular
respiration.